DESCRIPTION: (applicant's abstract) The long range goal of this research is to create a method for detecting specific base sequences in natural DNA and RNA that utilizes stable reagents, requires no instrumentation, and is rapid, reliable, inexpensive, sensitive at low target concentrations, and very simple to employ. Such a method could have an impact on health care throughout the world by facilitating early diagnosis, and thereby treatment, of diseases. The research proposed here stems from a collaboration that has led to a functional Prototype for a method for identification of oligonucleotides that exhibits a number of these desired features. This system exploits a new concept in detection based on changes in color accompanying the reversible formation of network assemblies from gold nanoparticle-oligonucleotide conjugates and complementary target oligonucleotides. To move forward and accomplish the long range goal, the investigators propose to build from this base by following three lines of research with the specific aims: (i) to build a firm scientific base for understanding the surface chemistry involving nanoparticle (colloids), nanoparticle-oligonucleotide conjugates, and oligo-and polynucleotides; (ii) to use this knowledge to develop a simple and rapid system applicable for direct detection of medically relevant targets, or in cases of very low target concentrations, of segments amplified by PCR; (iii) to create a signal amplification system based on sandwich assembly of probes, targets, and nanoparticle-liposome complexes, with capacity to identify directly very low concentrations of DNA and RNA containing specified sequences.